Method of preparing an aluminum alloy

ABSTRACT

A method of preparing an aluminum alloy which may be subsequently manufactured into an electrically conductive wrought product comprising the steps of preparing a pure aluminum melt in a first furnace and a scrap aluminum melt in a second furnace, charging melts from both the first furnace and the second furnace into a third furnace to produce a third melt having alloy constituents which fall within a prescribed formula, and fluxing the third melt. The present method permits the use of relatively inexpensive scrap materials to produce a useful material which may be formed into electrically conductive wrought products.

llnited States Patent Inventor Daniel B. Cofer Carrollton, Ga.

Appl. No. 848,1 12

Filed Aug. 6, 1969 Patented Dec. 28, 197 l Assignee Southwlre Company Carrollton, Ga.

Continuation-impart of application Ser. No. 608,507, Jan. 1 l, 1967, now abandoned which is a continuation-in-part of application Ser. No. 557,392, June 14, 1966, now abandoned. This application Aug. 6, 1969, Ser. No. 848,1 12

METHOD OF PREPARING AN ALUMINUM ALLOY 8 Claims, No Drawings Primary Examiner-Richard 0. Dean Attorney-Jones & Thomas ABSTRACT: A method of preparing an aluminum alloy which may be subsequently manufactured into an electrically conductive wrought product comprising the steps of preparing a pure aluminum melt in a first furnace and a scrap aluminum melt in a second furnace, charging melts from both the first furnace and the second furnace into a third furnace to produce a third melt having alloy constituents which fall within a prescribed formula, and fluxing the third melt. The present method permits the use of relatively inexpensive scrap materials to produce a useful material which may be formed into electrically conductive wrought products.

METHOD OF PREPARING AN ALUMINUM ALLOY CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of my copending application, Ser. No. 608,507 filed Jan. 11, 1967, now abandoned which was in turn a continuation-in-part of my copending application, Ser. No. 557,392, filed June 14, 1966, now abandoned.

DISCLOSURE This invention relates to a method of preparing an aluminum alloy and more particularly to a method of producing an aluminum alloy from portions of scrap aluminum containing typical impurities.

There is a frequent requirement within the industry that an aluminum wire or other wrought aluminum alloy product have a particular conductivity in excess of 61 percent of the International Annealed Copper Standard (IACS). The particular percentage conductivity requested is generally achieved by employing substantially pure aluminum in the wire or product in order to achieve the greatest conductivity available even though that conductivity is often greater than the conductivity requested. As might be expected, substantially pure aluminum is considerably more expensive than scrap aluminum containing typical impurities. In addition, substantially pure aluminum has decreased tensile strength, percent elongation and ductility when compared to various scrap aluminum alloys. Thus, if scrap aluminum alloy could be blended in such a fashion to produce an aluminum alloy which could be manufactured into a particular product having substantially the same conductivity as requested, a great savings in cost and convenience could be effected and the final product could most likely have improved properties when compared to a product manufactured from substantially pure aluminum.

It is, therefore, an object of the present invention to provide a method whereby portions of scrap aluminum alloy are blended to produce an alloy melt which may be subsequently worked into a product having a required conductivity. This and other objects, features and advantages of the presentinvention will become apparent from a review of the following detailed description of several embodiments of the invention.

According to the present invention, it has been found that scrap aluminum alloy may be converted into a desired alu minum alloy by maintaining proper relationships among elements in the aluminum alloy melt. In the past, it has been customary to prepare an aluminum alloy for casting in a substantially pure form in order to maximize the electrical conductivity of wrought products prepared from the casting. Many times it is not necessary to maximize conductivity since a conductivity less than maximum will satisfy the requirements of the industry. By the present method it is possible to achieve, within reasonable limits, a prescribed electrical conductivity through the use of scrap aluminum alloy. In order to obtain an aluminum alloy cast metal having those properties required for subsequent working of the cast metal into a wrought aluminum alloy product having a particular percentage conductivity, it is necessary to closely control the elements in the cast metal so that a proper relationship is maintained. This relationship is achieved during blending of the molten metal from which the solidified aluminum alloy cast metal is prepared.

By closely controlling the alloying elements, it is also possible to improve the physical properties of the final wrought product in areas other than conductivity. Thus, the castability, ultimate elongation, ductility and like properties may be improved.

The aluminum alloy of the present invention contains primarily the element aluminum and varying percentages by weight of some or all of the elements from a group of alloying elements including iron, copper, silicon, titanium, boron, vanadium, chromium, maganese, gallium, zinc, and magnesium. These elements are customarily found in aluminum and aluminum alloy metals and they serve to alter the physical properties of the metal in varying degrees depending on their concentration and their ratio to one another.

It should be understood that most scrap aluminum alloy metals available for use in blending a molten metal contain a significant number and amount of the above-described elements, and that most casting ingots (conventionally considered to be substantially pure) which are available for this purpose contain only slight amounts of some of the elements. Consequently, ingots have been used in the past almost exclusively in the blending of molten metal to provide an aluminum alloy even though scrap metals are generally less expensive than ingots.

Specifically, according to one form of practicing the present invention, a first melt containing scrap aluminum alloy is prepared in a first furnace. In a second furnace a second melt containing relatively pure aluminum (such as from an ingot) is prepared. A third melt in a third furnace is then prepared by charging the third furnace from the first and second furnaces so that the percentages by weight of the alloying elements in the third melt fall within the following formula:

Where x is the selected conductivity desired, y is one of two constants depending upon the value of x, and T is the tensile strength to be achieved in the final wrought product by processing of the product. The two constants for y are 64.9 when x is 61.9 to 62.5% lACS, and 65.2 when x is 61.0 to 61.89% IACS. Thus, the formula for alloying elements in the final melt is one of the following depending upon what conductivity is desired for the final wrought product.

(1) 8(%Cu %Fe) 20(%Si) (%Ti %V %Cr %Mn) 2(%Ga Zn) 25(%Mg) 64.9 (a figure selected from 61.9 to 62.5) 1 6,000T)/ 10,000

(2) 8(%Cu %Fe) 20(%Si) 90(%Ti %V %Cr %Mn) 2(%Ga %Zn) 25(%Mg) 65.2 (a figure selected from 61.0 to 61.89) l6,0007)/10,000

After charging melts from furnaces number 1 and number 2 to achieve an appropriate melt in furnace number 3, the number 3 melt can be fluxed in conventional fashion so as to be ready for pouring into a casting mold such as the mold defined between a circular groove in the periphery of a rotating wheel and a band positioned adjacent the wheel groove at and below the pouring level of the molten aluminum. Those skilled in the art will immediately recognize that my invention can be practiced using different furnace charging procedures, such as by omitting furnaces l and 2 and merely charging furnace 3 directly with properly proportioned amounts of scrap and pure aluminum. Furnace 3, having been charged in this manner in the first place thereby alleviating the need of furnaces l and 2 could, if necessary, be subsequently blended before casting with either pure aluminum, scrap aluminum, or another pure and scrap mixture, just so long as the proportions specified in the above formulas are maintained.

Thus, upon selecting a desired percentage conductivity between 61.0 and 62.5 (the practical limits for electrical conductivity in aluminum and aluminum alloy products) and a desired tensile strength for the final product, a single figure for the right-hand portion of the formula may be obtained. The concentrations of the various elements may then be varied within the formula to achieve a figure for the left-hand portion of the formula which equals or substantially equals the previously determined figure for the right-hand portion of the formula. From a brief review of the entire formula, it should be apparent that the concentrations of the various elements and the ratios of the individual elements one-to-another may be varied in many different relationships to produce different alloys and one may still obtain a final melt before casting which will have the desired electrical conductivity at the desired tensile strength.

It has been found that the content of aluminum in the final melt should be at least 99.45 percent by weight and the remaining 0.55 percent by weight or less should be alloying elements. of course, very often the percentage of aluminum is much higher, thus causing the total percentage of alloying elements to be much smaller. Even at these very small percentages for alloying elements through, the final physical properties of a wrought product prepared from the melt are significantly affected if a proper relationship is not maintained among all the alloying elements.

The present invention will be further described by the following examples.

EXAMPLE I An aluminum alloy cast metal is prepared so that wrought products manufactured therefrom will have a conductivity of 62.3 percent lACS when the wrought product has a tensile strength of 16,000 pounds per square inch A first melt is prepared in a first furnace and a second melt is prepared in a second furnace. Three thousand pounds of the first melt and 16,000 pounds of the second melt are added to a third furnace to produce a third melt weight of 19,000 pounds. The constituencies of the melts are such that the following amounts of individual elements are added together to achieve the third melt:

Weight pereent 01 elements First melt Second melt Third melt in third Element in pounds in pounds in pounds melt Al 2, 003. 52000 15, 062. 06472 18, 055 58472 00. 76654 11 V .45000 1. 551-15 2. 00145 01053 (n 15000 1. 50042 1. 65042 00860 Fe 3. 00000 20. 71340 24. (11340 12054 Hi 1. 50000 0. 50783 11. 18783 0588B '11 03008 03008 .00021 V .03000 03008 00021 ('1'. 15008 15008 0008-1 Mn. 00000 18313 27313 .00144 (121, 24000 1. 20615 1. 44615 00761 Zn 1 V 2. 78208 2. 78208 .01465 Mg. 06000 15008 21008 .00116 Tot-.11 16, 000. 00000 10, 000. 00000 The relationship among elements in the third melt is as defined by formula (1 and such is shown by inserting the percentages by weight of the elements in the formula with x, equal to 62.3, y equal to 64.9, and Tequal to 16,000. The formula then becomes:

The figure 2.5996 is so close to the figure 2.6 that the two are accepted as equal.

EXAMPLE 11 Example 1 is repeated except that a different aluminum alloy is used to prepare the second melt. The constituencies of the melts are such that the following amounts of individual elements are added together to achieve the third melt:

By inserting the above figures in the formula with x equal to 62.3, y equal to 64.9 and T equal to 16,000, the following is obtained:

+25(0.00383)=2.6+0; 1.14646+1 .01800+O.29700+0.04625+0.09575=2.6; 2.60356=2.6. The figure 2.60356 is so close to the figure 2.6 that the two are accepted as equal.

EXAMPLE Ill An alumlnum alloy cast metal is prepared so that wrought products manufactured therefrom will have a conductivity of 61.3% lACS when the wrought product has a tensile strength of 16,000 pounds per square inch. A first melt is prepared in u first furnace and a second melt is prepared in a second furnace. Three thousand pounds of the first melt and 16,000 pounds of the second melt are added to a third furnace to produce a third melt weighing 19,000 pounds. The constituencies of the melts are such that the following amounts of individual elements are added together to achieve the third melt:

Weight pereent of elements First melt Seeondmelt Third melt 1n third Element in pounds in pounds in pounds melt EXAMPLE 1V Example 111 is repeated except that a different aluminum alloy is used to prepare the second melt. The constituencies of the melts are such that the following amounts of individual ,0 elements are added together to achieve the third melt:

Weight Weight percent of pen-ent of elements elements First melt Second melt Third melt in third First. melt Second nielt 'Ihird melt in third Element in pounds in pounds in pounds melt Element in pounds in pounds in pounds melt A1 a 2, 003. 52000 15, 1162. 02857 18, 055. 54857 00. 70603 A1 1 2, 0113. 52000 15, 037. 41652 111, 030. 03652 00. 03052 11 a v a 45000 1. 71743 2.16743 01141 11 1 1 45000 1. 45016 1. 00010 01000 W 1 a 1 V 1 3. 00000 21. 24360 25. 14360 13233 Fe 3. 00000 42. 22322 40. 12322 24275 31 V 1 a 1 1. 50000 8. 08056 0. 67050 05000 Si 1 1. 50000 0. 110000 11. 30000 06000 '11. 07500 07500 V 15084 15084 .00084 07500 075 16084 15084 0008-1 15000 15000 15084 15084 00084 Total 1 3, 000. 00000 16 000. 00000 10, 000. 00000 100. 00000 Total 1 3, 000. 00000 16. 000. 00000 10, 000. 00000 100. 00000 By inserting the above figures in the formula with x equal to 61.3, y equal to 65.2 and Tequal to 16,000 the following is obtained:

0 .00084 l- 0.00084+ 0.00084+0.00248) f2( 000982 50510835)-l-(0.00299)?65 2 6 1 .3+(16,000 16',000);/ 10,000 m"- The relative freedom, provided by the method of the present invention, in the selection of the melts which are used in preparing the third melt permits the usage of relatively inexpensive scrap material and also permits the creation of various alloys having different physical properties. Specifically, in all four alloys of the examples, less than 0.06 percent of copper is added to the third melt. Thus, all four of the alloys have good castability as molten metals and good working properties as aluminum alloy cast metals. It has also been found that in preparing an aluminum alloy melt as discussed herein, the ratio of the percentage by weight of iron to the percentage by weight of silicon may range from 2:1 to 6:1. Those skilled in the art will recognize that this freedom with respect to iron and silicon provides effective control of the castability of the aluminum alloy melt.

it should be noted also that the present method provides an aluminum alloy melt in which the percentage by weight of boron may be in excess of 0.003 percent. Thus, good castability of the melt is further insured and the percentage by weight of silicon may be independent of its ratio to the percentage by weight of iron. Those skilled in the art will recognize that freedom in the relationship between iron-silicon ratio and the percentage by weight of silicon in the melt insures that the aluminum alloy melt has good tensile strength while also having good castability as a molten metal.

For purposes of clarification, it should be understood that substantially pure aluminum normally has the following maximum concentration of impurities:

Ti, .0O3;V, .003; Mg, .003; Si, .05; B, .02, Ga, .015; Cu, .01; Fe, .10; Ni, .003

Or, .003; Mn, .003

It should also be understood that the range of tensile strengths for electrically conductive aluminum alloy products is generally 12,000 p.s.i. to 27,000 p.s.i. In addition, whenever the expressions wrought product," wrought aluminum product," or wrought aluminum alloy product" are used in this description, the expressions are referring to a product which has been subjected to mechanical working by such processes as rolling, extruding, forging and the like. Such products include flat and round wire of various gauges and sheet stock.

While this invention has been described in detail with particular reference to preferred embodiments thereof, it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinbefore and as defined in the appended claims.

lclaim:

1. Method of preparing an aluminum alloy which may be subsequently cast and worked to a final product having a predetermined electrical conductivity and a predetermined tensile strength comprising charging a furnace with relatively pure aluminum and scrap aluminum alloys containing one or more of copper, iron, silicon, titanium, boron, vanadium, chromium, manganese, gallium, zinc, and magnesium and the remainder aluminum and blending the mixture so that the melt created within the furnace has elemental constituents, other than aluminum, which fall within the ranges for elemental constituents provided by the following formula:

8(%Cu %Fe) 20(%Si) (%Ti %V %Cr %Mn) 2(%Ga %Zn) 25(%Mg) by (16,000-T );/l0,000 wherein x is 64.9, y represents the predetermined electrical conductivity and is selected from the figures 61.9 to 62.5, and T represents the predetermined tensile strength and is selected from the figures 12,000 p.s.i. to 27,000 p.s.i.

2. Method of preparing an aluminum alloy as described in claim 11 including the additional step of fluxing the furnace melt so that it may be subsequently cast into a segmented or continuous bar.

3. Method of preparing an aluminum alloy as described in claim 1 wherein the furnace is charged with relatively pure aluminum having less than 0.003 wt. Ti, 0.003 wt. V, 0.003 wt. Mg. 0.05 wt. Si, 0.02 wt. B, 0.015 wt. Ga, 0.01 wt. Cu, 0.10 wt. Fe, 0.003 wt. Ni, 0.003 wt. Cr, and 0.003 wt. Mn and the remainder aluminum and a scrap aluminum alloy having more than 0.003 wt. Ti, 0.003 wt. V, 0.003 wt. Mg, 0.05 wt. Si, 0.02 wt. B, 0.015 wt. Ga, 0.01 wt. Cu, 0.10 wt. Fe, 0.003 wt. Ni, 0.003 wt. Cr, and 0.003 wt. Mn and the remainder aluminum to achieve a final aluminum melt having elemental constituents according to the formula.

4. Method of claim 3 comprising preparing a first aluminum melt of relatively pure aluminum in a first furnace, preparing a second scrap aluminum alloy melt in a second furnace, and subsequently charging melts from the first and second furnaces into a third furnace to create a third melt having elemental constituents, other than aluminum, which fall within the ranges for elemental constituents provided by the formula.

5. Method of preparing an aluminum alloy which may be subsequently cast and worked to a final product having a predetermined electrical conductivity and a predetermined tensile strength comprising charging a furnace with relatively pure aluminum and scrap aluminum alloys containing one or more of copper, iron, silicon, titanium, boron, vanadium, chromium, manganese, gallium, zinc, and magnesium and the remainder aluminum and blending the mixture so that the melt created in the furnace has elemental constituents, other than aluminum, which fall within the ranges for elemental constituents provided by the following formula:

+2(%Ga %Zn) 25(%Mg) x y (16,000 T) 10,000 wherein x is 65.2, y represents the predetermined electrical conductivity and is selected from the figures 61.0 to 61.89, and T represents the predetermined tensile strength and is selected from the figures 12,000 p.s.i. to 27,000 p.s.i.

6. Method of preparing an aluminum alloy as described in claim 5 including the additional step of fluxing the furnace melt so that it may be subsequently cast into a segmented or continuous bar.

7. Method of preparing an aluminum alloy as described in claim 5 wherein the furnace is charged with relatively pure aluminum having less than 0.003 wt. Ti, 0.003 wt. V, 0.003 wt. Mg, 0.05 wt. Si, 0.02 wt. 8, 0.015 wt. Ga, 0.01 wt. Cu, 0.10 wt. Fe, 0.003 wt. Ni, 0.003 wt. Cr, and 0.003 wt. Mn and the remainder aluminum and a scrap aluminum alloy having more than 0.003 wt. Ti, 0.003 wt. V, 0.003 wt. Mg, 0.05 wt. Si, 0.02 wt. B, 0.015 wt. Ga, 0.01 wt. Cu, 0.10 wt. Fe, 0.003 wt. Ni, 0.003 wt. Cr, and 0.003 wt. -Mn and the remainder aluminum to achieve a final aluminum melt having elemental constituents according to the formula.

0. Method of claim 7 comprising preparing a first aluminum melt of relatively pure aluminum in a first furnace, preparing a second aluminum melt of a scrap aluminum alloy in a second furnace, charging melts from the first and second furnaces into a third furnace to create a third melt having elemental constituents, other than aluminum, which fall within the ranges for elemental constituents provided by the formula, the remainder of said third melt constituting aluminum.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,630,725 Dated Dgggmbg; 23 7;

Inve H D. B. Cofer It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In Column 3, Line 66, the number ".10199" should appear as --.0l099.

In Column 4, Line 4, the number "0.5090" should appear as -0. 05090-.

In Column 4, Line 5, the number "0.012373" should appear as 0.0l273-.

Signed and sealed this 13th day of March 1973.

sEALj Attest:

EDWARD M.FLETCHER,JR. I ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents FORM po'wso USCOMM-DC 60376-P69 Q US GOVERNMENT PRINTING OFFICE: I969 O-366-334 

2. Method of preparing an aluminum alloy as described in claim 1 including the additional step of fluxing the furnace melt so that it may be subsequently cast into a segmented or continuous bar.
 3. Method of preparing an aluminum alloy as described in claim 1 wherein the furnace is charged with relatively pure aluminum having less than 0.003 wt. % Ti, 0.003 wt. % V, 0.003 wt. % Mg. 0.05 wt. % Si, 0.02 wt. % B, 0.015 wt. % Ga, 0.01 wt. % Cu, 0.10 wt. % Fe, 0.003 wt. % Ni, 0.003 wt. % Cr, and 0.003 wt. % Mn and the remainder aluminum and a scrap aluminum alloy having more than 0.003 wt. % Ti, 0.003 wt. % V, 0.003 wt. % Mg, 0.05 wt. % Si, 0.02 wt. % B, 0.015 wt. % Ga, 0.01 wt. % Cu, 0.10 wt. % Fe, 0.003 wt. % Ni, 0.003 wt. % Cr, aNd 0.003 wt. % Mn and the remainder aluminum to achieve a final aluminum melt having elemental constituents according to the formula.
 4. Method of claim 3 comprising preparing a first aluminum melt of relatively pure aluminum in a first furnace, preparing a second scrap aluminum alloy melt in a second furnace, and subsequently charging melts from the first and second furnaces into a third furnace to create a third melt having elemental constiteunts, other than aluminum, which fall within the ranges for elemental constituents provided by the formula.
 5. Method of preparing an aluminum alloy which may be subsequently cast and worked to a final product having a predetermined electrical conductivity and a predetermined tensile strength comprising charging a furnace with relatively pure aluminum and scrap aluminum alloys containing one or more of copper, iron, silicon, titanium, boron, vanadium, chromium, manganese, gallium, zinc, and magnesium and the remainder aluminum and blending the mixture so that the melt created in the furnace has elemental constituents, other than aluminum, which fall within the ranges for elemental constituents provided by the following formula: 8(%Cu + Fe) + 20(%Si) + 90(%Ti + %V + %Cr + %Mn) +2(%Ga + %Zn) + 25(%Mg) x-y + (16,000- T)/10,000 wherein x is 65.2, y represents the predetermined electrical conductivity and is selected from the figures 61.0 to 61.89, and T represents the predetermined tensile strength and is selected from the figures 12,000 p.s.i. to 27,000 p.s.i.
 6. Method of preparing an aluminum alloy as described in claim 5 including the additional step of fluxing the furnace melt so that it may be subsequently cast into a segmented or continuous bar.
 7. Method of preparing an aluminum alloy as described in claim 5 wherein the furnace is charged with relatively pure aluminum having less than 0.003 wt. % Ti, 0.003 wt. % V, 0.003 wt. % Mg, 0.05 wt. % Si, 0.02 wt. % B, 0.015 wt. % Ga, 0.01 wt. % Cu, 0.10 wt. % Fe, 0.003 wt. % Ni, 0.003 wt. % Cr, and 0.003 wt. % Mn and the remainder aluminum and a scrap aluminum alloy having more than 0.003 wt. % Ti, 0.003 wt. % V, 0.003 wt. % Mg, 0.05 wt. % Si, 0.02 wt. % B, 0.015 wt. % Ga, 0.01 wt. % Cu, 0.10 wt. % Fe, 0.003 wt. % Ni, 0.003 wt. % Cr, and 0.003 wt. % Mn and the remainder aluminum to achieve a final aluminum melt having elemental constituents according to the formula.
 8. Method of claim 7 comprising preparing a first aluminum melt of relatively pure aluminum in a first furnace, preparing a second aluminum melt of a scrap aluminum alloy in a second furnace, charging melts from the first and second furnaces into a third furnace to create a third melt having elemental constituents, other than aluminum, which fall within the ranges for elemental constituents provided by the formula, the remainder of said third melt constituting aluminum. 